1. Field of the Invention
The present invention relates to the technical field of fluid pressure measurement and in particular to the manufacturing of a component for a fluid pressure measurement unit, like, e.g., those used for blood pressure measurement by pressure transmission by means of a liquid column, like the liquid in a pressure measurement tube or a pressure measurement line, respectively.
2. Description of Related Art
In order to cause the least possible effort in hospitals or clinics in the care of patients, there is an increasing interest in combining different measurement and diagnosis systems with each other, in order to hereby on the one hand deal with an excessive fear of patients with regard to an excessive use of technical gear and on the other hand also to guarantee a clearer arrangement of medical apparatus' for medical personnel. In particular, there are great efforts ongoing to reduce the conventionally used plurality of cables and lines in order to guarantee a clearer arrangement of the individual lines to or from the patient in order, in particular, to also exclude a possible wrong handling of medical systems by a “mixing up” of the cables and lines. In this connection, a blood pressure measurement has already been integrated into an infusion system, wherein the fact was used that the liquid column from the arterial or venous catheter (not shown) to a pressure gauge may be used as a pressure transmission medium when a sufficiently form-stable tube between venous/arterial catheter and pressure gauge is used. The blood pressure is then transmitted via the infusion solution from an artery or vein via the catheter and via the so-called form-stable tube to a special sensor which is implemented to detect pressure variations in the infusion solution which then correspond to the blood pressure values to be measured. Such a pressure sensor is also called a transducer.
The basic setup of such an infusion system with the functionality of a blood pressure measurement is illustrated in FIG. 3. Such a system comprises an infusion solution bag 302 which is connected to a first tap or rinsing system 102 via an infusion solution tube 304. The rinsing system is provided with a capillary serving as a pressure decoupling of the further system components from the infusion solution bag 302. The rinsing system 102 may here be designed such that it guarantees a predefined flow rate of, for example, 3 ml per hour.
The first tap or the rinsing system 102, respectively, is connected to a transducer 100 which may again be connected to a second tap 104. The second tap 104 is connected to the patient 311 via a pressure-stable pressure measurement line 310 (for example via a catheter). Here it is to be noted, that that the pressure measurement line 310 illustrated in FIG. 3 should comprise a high form stability or rigidity, i.e. a low elasticity, in order not to corrupt or dampen pressure variations.
The second tap 104 is normally used for “zeroing”, i.e. for setting or calibrating the pressure to be measured at the transducer 100 with respect to atmospheric pressure, by providing the tap 104 of the transducer 100 with atmospheric pressure while decoupled from the patient.
A known type of transducer in pressure measurement systems consists of several individual parts. A typical setup of such a conventional transducer is given in the sectional view in FIG. 4.
According to FIG. 4, the conventional transducer comprises a bottom housing part 402 (for example in cup shape), in which a pre-formed membrane 404 (for example made of silicon) is inserted. Onto the membrane 404 a contact carrier 406 is seated, comprising openings 408 into which socket contacts 410 with contact springs are pressed.
Further, the bottom housing part 402, the membrane 404 and the contact carrier 406 comprise a central hole 409, through which an atmospheric pressure of the exterior environment of the transducer is applied to a top area of the contact carrier 406.
The contact springs are soldered to terminal contacts 412 on the ceramic plate 414, wherein the contact terminals 412 are connected to contacts of a measurement chip 416. The measurement chip 416 is here arranged on a first side of the ceramic plate 414 above an opening in the ceramic plate 414, which is part of the central hole 409, wherein the terminal contacts 412 are arranged at a second side of the ceramic plate 414 opposite the first side.
Further, an O-ring 415 is arranged between the contact carrier 406 and the ceramic plate 414 laterally surrounding the opening 409 in the contact carrier 406. Hereby, for an atmospheric pressure compensation, an ambient air pressure is applied to the measurement chip 416 as a reference value via the central hole 409 or the opening in the ceramic plate 414, respectively. Further, by the O-ring 415 a sealing of the socket contacts or the electric connections, respectively, like the terminal contacts 412 or conductive traces on the ceramic plate 414, against conductive liquids is provided, like for example the infusion solution or liquids applied from the outside, which might enter into the interior of the housing when connecting the transducer.
Further, the transducer comprises a top housing part 418 including a flow channel 420 for the infusion solution. The measurement chip 416 is here arranged in a recess of the flow channel 420. In addition, the measurement chip is covered by a gel, protecting the measurement chip 416 against the infusion solution, as with a direct contact of the electrically conductive infusion solution with the measurement chip 416 a corruption of the measurement results by “creeping currents” would occur in the electrically conductive infusion solution. Via the gel, however, pressure variations may be transmitted in the fluid to the measurement chip 416. Further, the top housing part 418 is connected to the bottom housing part 402 at welding or splice points 422 (for example via an ultrasonic welding), so that the transducer in its final form is produced.
A connection of the transducer is now performed such that a socket or a socket connection 424, respectively, is passed via an opening into the floor of the bottom housing part 402 through the membrane 404 and brought into connection with the contact springs of the socket contacts 410 in an electrically conductive way. For this process, for example, the membrane 404 is already provided with slots, which strip off possibly present liquids at the socket pins when plugging in the connection plug 424.
Due to the high number of individual parts, the manufacturing process for the type of transistor illustrated in FIG. 4 is cost- and time-consuming. A possible manufacturing process here, for example includes the following steps.
First of all, in the manufacturing of a transducer, the socket contacts 410 are pressed into the contact carrier 406. Subsequently, the O-ring 415 is seated onto this contact carrier 406 provided with the socket contacts 410, whereupon the ceramic plate 414 (hybrid ceramic with imprinted conductive traces and resistances) is put onto the O-ring 415. The measurement chip 416 is attached to the ceramic place 414 with the corresponding terminal contacts 412. After seating the hybrid ceramic onto the O-ring 415 and the contact carrier 406, soldering tags 411 of the socket contacts 410, pressed into the contact carrier, are connected and soldered to the terminal contacts 412 of the hybrid ceramic. Due to the high temperatures occurring during soldering, the contact carrier 414 has to be manufactured from an especially temperature- and form-stable material, which is cost- and time-consuming and also limits the selection of material candidates with respect to other desired material characteristics. After the contacting, the membrane 404, for example as a sealing membrane made of silicon material, is inserted into the bottom housing part 402, in order to be clamped in between the contact carrier 406 and the bottom housing part 402. By this, the socket contacts 410 pressed into the contact carrier 406 are additionally sealed from the bottom. The membrane 404 is here a pre-manufactured silicon membrane which is used as an individual part in the manufacturing of such a transducer. Hereupon, a joining of the bottom housing part 402 with a top housing part 418 is performed, GO whereby the membrane 404 is clamped in, as described above. The bottom housing part 402 may be welded to the top housing part 418 using ultrasonics at the welding spot 422 or also be connected to the top housing part 418 using adhesives or solvents. Welding using ultrasonics enables a high tightness of the connection, is very cost- and times consuming, however, as a tight connection of the top housing part 418 and the bottom housing part 402 of the transducer has to be guaranteed, so that no liquid may enter into the transducer housing. This could lead to an electrical connection between the contacts and to a drift of the pressure measurement signal. Thus, it is required to perform a special examination of the tightness between the top housing part 418 and the bottom housing part 402, which is time-consuming and in particular in mass production of such transducers also costly. Finally, a gel is filled into the recess of the flow channel 420 to seal the sensor 416 watertight against the infusion solution, however to simultaneously enable a pressure transmission from the fluid in the flow channel 120 to the sensor 416. This filling in may, however, due to reasons of manufacturing technology, only take place by means of a cost- and time-consuming method using a syringe through the flow channel 120.